Cox blocking emails from a friends IP address

A good friend of ours is having a problem when he tries to send us and email.  His emails to us are delayed and he receives a notification that they have been rejected by Cox, citing error code CDRBL.  I understand that this error code means the the sending IP address has been temporarily blocked for exhibiting the characteristics of SPAM.

My friend is not a spammer.  He is, however, fond of forwarding emails to his many friends and family.

Is there any way that I can ask Cox to stop blocking emails from him?  I can provide his email address and IP address to Cox.